Light-emitting semiconductor device

Abstract

A flip-chip type of Group III nitride based compound semiconductor light-emitting device comprises a transparent conductive film 10 made of ITO on a p-type contact layer. On the transparent conductive film, an insulation protection film 20, a reflection film 30 which is made of silver (Ag) and aluminum (Al) and reflects light to a sapphire substrate side, and a metal layer 40 made of gold (Au) are deposited in sequence. Because the insulation protection film 20 exists between the transparent conductive film 10 and the reflection film 30, metal atoms comprised in the reflection film 30 can be prevented from diffusing in the transparent conductive film 10. That enables the transparent conductive film 10 to maintain high transmissivity. As a result, a light-emitting device having high external quantum efficienty can be provided.

Description

[0001]This is a patent application based on Japanese patent applications No. 2004-288880 and 2004-284075 which were filed on Sep. 30, 2004, and Sep. 29, 2004, respectively, and which are incorporated herein by reference.TECHNICAL FIELD [0002]The present invention relates to a light-emitting semiconductor device. Especially, the present invention relates to a flip-chip type light-emitting device which radiates lights from a transparent substrate side, having improved external quantum efficiency and suppressed age-related deterioration.[0003]Especially, the present invention relates to a light-emitting semiconductor device comprising a gallium nitride based compound semiconductor. Especially, the present invention relates to materials and structure of an electrode having electrically and optically excellent reliability about a flip-chip type of a light-emitting semiconductor device.BACKGROUND ART[0004]Progress in a light-emitting semiconductor device is remarkable in these days. Espec...

AI Technical Summary

Benefits of technology

[0051]Effects to be obtained by the present invention are explained as follows.

[0052]The insulation protection film suppresses interface reaction of the reflection film and the transparent conductive film. As a result, a driving voltage can be prevented from increasing. When the first electrode layer is a transparent conductive film, both transparency of the transparent conductive film and reflectivity of the reflection film can be prevented from decreasing. Then luminous output efficiency of lights outputted through the light-transmitting substrate can be improved.

[0053]When electricity is conducted, electric current flows into the transparent conductive film only from the contact part of the electrode layer and the transparent conductive film owing to the insulation protection film. That enables to remarkably decrease possibility of generating electromigration of the reflection film. When the entire surface of the reflection film is covered by the insulation protection film, electromigration of the reflection film can be prevented from generating more certainly.

[0054]In the present invention, the materials of the first electrode layer can be different from that of the reflection film. So the metal used to form the first electrode layer can be replaced with a material which has excellent ohmic contact to the contact layer, and that enables to reduce driving voltage of the light-emitting device.

[0055]According to another aspect of the present invention, the first electrode layer is formed to expose a portion of the contact layer. That enables to pass light emitted from the active layer through the exposed portion of the contact layer, reflect the light effectively by the reflection film having high reflectivity, return the light to the semiconductor layer, and finally radiate to the outside of the device through the light-transmitting substrate. Further, this electrode has structure in which the light-transmitting insulation protection film prevents the reflection film having high reflectivity from contacting electrically to the first electrode layer and to the contact layer. As a result, driving voltage increase owing to alloying of metal atoms comprised in the reflection film and metal atoms comprised in the first electrode layer may not occur, and the interface between the semiconductor and the first electrode layer doest not change. Accordingly, materials and structure of the electrode is comprehensively excellent in electricity, optics, and reliability.

Problems solved by technology

Generally, because of a Schottky barrier existing at the interface between the compound semiconductor and the metal, the compound semiconductor comprising a gallium nitride based compound semiconductor layer can hardly obtain ohmic characteristic only by depositing a metal electrode on a semiconductor layer.

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